<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>01_JS的三种引入方式</title>
</head>
<body>
  <button onclick="alert('请先登录')">点击登录</button>
  <button onclick="console.log('点我干嘛')">点我</button>
  <h1 id="aaa">我是一级标题</h1>
<script>
  console.log('我是内部JS，我被执行了！')
  console.log(aaa);
</script>
</body>
</html>
